1. Field of the Invention:
This invention relates to optical communication systems. More particularly, this invention relates to a method and apparatus for diverting an optical signal used in optical communications from a wave-length division multiplexed signal.
2. The Prior Art:
Because of the increased demands being placed on optical fiber transmission, various schemes of placing an increased number of communications on a single optical fiber have been employed in recent years. One method is time division multiplexing, in which different transmissions share the same fiber, but at different times. Another method is wavelength division multiplexing, in which different signals are modulated onto different wavelengths and are then combined to generate a signal that is transmitted over a single fiber. At the receiving end, the different wavelengths are separated, thereby regenerating the original signals.
As shown in FIG. 1, certain prior art wavelength division multiplexed optical communications systems 1 use a dense wavelength division multiplexer (DWDM) 3 to combine a plurality of signals 2, wherein each signal is centered about a different wavelength bandwidth xcex1-xcexz. The combined signal is transmitted from the DWDM 3 over an optical channel 6, such as an optical fiber, to a second DWDM 4 that is configured so at to separate the different wavelength bandwidth channels from each other, thereby rendering a reconstruction of the plurality of signals 5.
When one wants to analyze the transmission of a single wavelength transmission from such a DWDM signal, an optical add-drop multiplexer (OADM) 7 may be inserted into the optical channel 6. The OADM 7 separates from the signal a selected wavelength and transmits it to an analyzer 8.
This arrangement has the disadvantage of adding increased cost due to the plurality of OADM""s that must be employed in a multi-fiber network. Furthermore, the prior art has the disadvantage in that if a single OADM fails, it could disrupt the communications of many different signals.
Nowhere does the prior art disclose a method or apparatus that allows access to an OADM""ed optical signal being transmitted over an optical fiber without interrupting the communications over the optical fiber.
The above-noted disadvantages of the prior art are overcome by the present invention, which in one aspect is a system for diverting an optical component signal from a multiplexed optical signal. The system includes an optical communications channel having a first portion and a second portion. A multiplexed optical signal having a plurality of component signals may be transmitted through the optical communications channel. Each component signal lies within a different optical bandwidth. The system also includes a branch optical channel comprising a first section and a second section. A signal diverter that optically couples the first portion of the communications channel to the second portion of the communications channel directs a diverted portion of the multiplexed optical signal into the first section of the branch optical channel. The signal diverter also allows a non-diverted portion of the multiplexed optical signal to propagate into the second portion of the optical communications channel. An optical wavelength separator that is optically coupled to the first section of the branch optical channel separates a selected component signal from the diverted portion of the optical signal. The optical wavelength separator also optically couples the selected component into the second section of the branch optical channel. A port that is optically coupled to the second section of the branch optical channel allows the optical coupling of an optical device to the second section of the branch optical channel.
Another aspect of the invention is a method of providing a component signal, of an optical signal having a plurality of wavelength component signals, to an optical device. In executing the method, a portion of the optical signal is diverted from the optical signal while allowing a substantial portion of the optical signal to propagate along an optical communications channel. A selected wavelength component signal is separated from the portion of the optical signal. Then, the selected component signal is optically coupled to an optical device.